Corn Production as Affected by Nitrogen Application Timing and Tillage

could be optimized using modified NT systems (including ST) and starter fertilizer. In Iowa Mallarino et al. (1999) Utilizing conservation tillage practices and increasing fertilizer N found that ST frequently increased early growth but seluse efficiency for corn (Zea mays L.) are necessary for optimizing dom increased corn grain yields compared with NT. growers’ profits and for minimizing loss of sediment and nutrients to Best Management Practices (BMPs) for N are complithe environment. A 3-yr study was conducted on a Nicollet clay loam (fine loamy, mixed, mesic, Aquic Hapludoll)–Webster clay loam (fine cated by residue management and tillage. Spring, preloamy, mixed, super active, Typic Endoquoll) soil complex in southern plant application of fertilizer N to medium and fineMinnesota to determine the effects of four tillage systems (no tillage, textured soils of the northern Corn Belt is considered to strip tillage, one-pass field cultivate, and chisel plow) and two N be a BMP with conventional tillage systems. However, application times on corn production following soybean [Glycine max spring preplant application of anhydrous ammonia to (L.) Merr.]. Anhydrous ammonia was applied at 123 kg N ha 1 either NT and ST is often considered undesirable by growers in late October when soil temperatures at 15 cm were generally below because of delayed planting and compaction concerns 10 C or in April before planting. Tillage system had a statistically on wetter soils. Moreover, preplant broadcast applicasignificant effect on corn production but showed no interaction with tion of urea and urea–ammonium nitrate (UAN) withthe N timing treatments. Maximum differences among tillage systems out a urease inhibitor is not an option with NT and were 4.3% for grain yield, 5.1% for silage yield, and 8.6% for total N uptake. In 1 yr, when April and May were wet and warm, grain ST systems because when left unincorporated these N yield and total N uptake were reduced 20 and 27%, respectively, with sources are susceptible to volatilization losses (Keller fall N. Apparent N recovery was reduced from 87% for spring N to and Mengel, 1986; Mengel et al., 1982). With a urease 45% for fall N. Corn production was not affected by time of N applicainhibitor surface applications of urea containing fertiliztion in the other 2 yr. Relative leaf chlorophyll, measured by a SPAD ers can still result in yield reductions due to immobilizameter at the V10, R1, and R3 growth stages, was highly correlated tion (Vetsch and Randall, 2000). to relative corn grain yield, and could be used as a diagnostic tool at Time of N application studies have been reported the V10 stage to determine sidedress N needs under non-irrigated extensively in the literature. The general conclusion conditions. Because the risk of N loss is greater with fall N application, among researches has been that N should be applied N should be applied in the spring on these soils to minimize risk and nearest to the time it is needed by the crop, i.e., sideoptimize profitability regardless of tillage system. dressed several weeks after corn emergence (Aldrich, 1984; Fox et al., 1986; Olson and Kurtz, 1982; Russelle et al., 1981; Stanley and Rhoades, 1977; Welch et al., T illage system and N application timing are impor1971). There is less time for leaching or denitrificatant management decisions that farmers make for tion losses when N is applied after plant emergence. corn production on the highly productive but poorly However, recent trends in agriculture which include indrained soils of the northern Corn Belt. Dominance of creased farm size, more farmers with off-farm jobs the corn–soybean rotation in this region is raising con(USDA-NASS, 1997, 1992), and greater use of postcern about sediment and nutrient contributions to suremerge herbicides, have left less time for farmers to face waters (Randall, 2002). Conservation tillage pracsidedress N. tices like no tillage (NT) are effective at managing crop Application of N in the fall has advantages for both residue to reduce erosion. However, widespread adopgrowers and the fertilizer industry. These economic and tion of NT for corn on glacial till soils in Minnesota logistical advantages include better distribution of labor (USA) has not occurred. Researchers have responded and equipment demands, time savings during the busy to grower concerns of reduced yield potential and lack spring planting season, lower N costs in some years, and of adoption of NT by studying modified NT systems frequently more favorable soil conditions for field work that conserve residue and are agronomically competi(Bundy, 1986; Randall and Schmitt, 1998). Comparisons tive with more conventional tillage practices. Randall of corn yield with fall or preplant N application have et al. (2001) showed that fall strip tillage (ST) for corn been variable. Fall application (mid-November) profollowing soybean produced greater yields than NT on duced lower corn grain yields than spring preplant applia clay loam soil in one of two studies and ST yields cation regardless of N rate in Ontario (Stevenson and were equal to conventional tillage (CP) in both studies. Baldwin, 1969). The yield reduction associated with fall On a silt loam soil Vetsch and Randall (2002) concluded application was greater on clay soils than on loam soils. that surface residue and corn yield following soybean Three-year yield averages showed fall application on medium-to-fine textured soils in central and northern Southern Research and Outreach Center, Univ. of Minnesota, 35838 Illinois to be 90% as effective as spring application at 120th St., Waseca, MN 56093-4521. Received 27 May 2003. *Corre134 kg N ha 1 with equal yields for fall and spring applisponding author ([email protected]). Abbreviations: CP, chisel plow tillage; NT, no tillage; OP, one-pass Published in Agron. J. 96:502–509 (2004).  American Society of Agronomy tillage (spring field cultivation); RLC, relative leaf chlorophyll; ST, fall strip tillage. 677 S. Segoe Rd., Madison, WI 53711 USA